Abstract
This paper describes a liquid metal-based multifunctional antenna capable of wideband frequency tuning, dual band operation, and polarization reconfiguration. The radiating elements consist of parasitically-excited plugs of room-temperature liquid metal in 3D printed channels. Syringe pumps flow the gallium-alloy plugs in proximity to a capacitive feeding structure. This non-contact feeding scheme separates the metal flow path from the SMA connector and lends mechanical robustness at the feed while allowing impedance matching over a wide range of frequencies. Sliding the plug along a right-angle bend enables linear polarization reconfiguration, while simultaneously placing plugs in both orthogonal channels can generate circular or 45° linear polarization. Dual band operation is also supported by infusing plugs of two dissimilar lengths into the two channels. Simulation and measurement results demonstrate that this antenna can tune its impedance over a decade (10:1 frequency range) maintaining a 2:1 VSWR and achieve a polarization diversity >12 dB. The pumped plugs can circulate at a peak velocity of 50 mm/s, currently limited only by our pumping equipment. Repeatability analysis is also performed by cycling the plug actuation more than 1100 times. More complex designs can exploit this design concept to develop new types of highly versatile, multi-functional antennas.
Highlights
As modern-day antenna systems are growing in complexity, reconfigurability of antenna characteristics such as frequency, pattern or polarization is becoming an important capability
Recent approaches for reconfigurable antennas include the use of metal alloys that exist in a liquid state at room temperature and can be reshaped to alter the electromagnetic response of the device
We describe a novel multifunctional LMbased planar antenna that combines 10:1 frequency tuning range and reconfigurable polarization
Summary
As modern-day antenna systems are growing in complexity, reconfigurability of antenna characteristics such as frequency, pattern or polarization is becoming an important capability. The planar antenna radiates like a narrow microstrip patch antenna and the peak gain is normal to the ground plane (along the z axis) With a low melting point of 15.5◦ C, this alloy exists in a liquid state at room temperature and has an electrical conductivity of 3.4x106 S/m, which is approximately 1/17th of that of copper [31] Plugs of this liquid metal are introduced and steered to form the metallized portion of the reconfigurable antenna geometry. Several channels with varying plug lengths can be used, as demonstrated in this work using two adjacent channels, but other methods to allow for rapid changes in plug length are the subject of current investigation
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